1. Field of the Invention
The present invention relates to an ink drop generator for ink-jet printers.
2. Description of the Prior Art
Ink-jet printers which have been produced hitherto comprise at least one ink drop generator which projects a series of drops towards the surface of the paper on which the printing is to appear. The drops are compelled by deflecting means to follow predetermined trajectories in order to form on the paper groups of dots representing images of characters or graphic designs of any kind.
Printers of this kind are known in which the drop generator is formed by a mechanical vibration amplifier formed by a nozzle of small dimensions having one end of large cross-section and one end of small cross-section and pierced by a central passage extending between these two ends. The passage receiving ink under pressure at its opening is situated at the large cross-section end of the nozzle and terminates as the other end of the nozzle in a very small ink ejection opening. An electromechanical converter device, which is generally formed by a piezoelectric crystal member and which is fixed against the end of larger cross-section of the nozzle, imparts to the nozzle when excited electrically, a longitudinal vibration movement. This vibratory movement causes the ink jet emerging from the nozzle to break up into drops. The electromechanical converter device is also attached, by the face opposite that in contact with the larger cross-section end of the nozzle, to a carrier block which in turn is secured to the frame of the machine. An ink drop generator of this kind is described and illustrated in French patent No. 2,204,149.
With a drop generator of this nature, it is difficult to prevent the vibrations of the nozzle from being retransmitted on the one hand to the electromechanical converter device and on the other hand to the supporting block. As a result, the two electrodes which are associated with the nozzle and with the electromechanical converter device, respectively, are subjected to vibrations and such vibrations can cause disconnection of the electrical conductors. There is also a danger that the vibrations, even though of small amplitude, may be transmitted to the framework of the machine via the supporting block and upset the vibratory movement of adjacent drop generators. It may be possible to prevent these vibrations from being transmitted to the framework of the machine by inserting a damping member, such as a slab of rubber for example, between the frame and the supporting block; however, there is the added disadvantage of transverse vibrations in the generator which would cause changes in the direction of the ink jet emerging from the nozzle.